1. Field of the Invention
The present invention relates to a driving apparatus for a linear compressor. More specifically, it relates to an apparatus for driving a linear compressor in which a piston is reciprocally moved in a cylinder by a linear motor for generating compressed gas.
2. Description of the Background Art
Recently, a linear compressor as a mechanism for compressing expanded refrigerant gas in a cooling apparatus such as a refrigerator has been developed. In the linear compressor, a piston is driven by a linear motor and a resonance mechanical spring, and the gas is compressed.
In such a linear compressor, non-linear force (spring force of gas) is generated in a compression phase in association with suction, compression and discharge of gas, and the non-linear force varies because of load variation at the time of activation, for example.
However, in a conventional linear compressor, there is not at all means for controlling thrust of the linear motor, and a constant electric power is supplied to the linear motor regardless of the load variation. Therefore, ratio of an output energy with respect to an input energy (hereinafter referred to as efficiency) has been low. Though a method of controlling voltage to be applied to a coil of the linear motor in accordance with the load variation has been studied, it is not satisfactory.